Critical Review by Michael Rowan-Robinson

In the following excerpt, Rowan-Robinson remarks favorably on The Nature of Space and Time.

Stephen Hawking and Roger Penrose are well-known both for their work on the nature of black holes and for successful books for the general public. The Nature of Space and Time has its origin in a series of lectures that they gave at a study programme in 1994 at the Isaac Newton Institute in Cambridge. They outline their past and current work on the global causal structure of space-time, singularity theorems, cosmic censorship, the laws of blackhole dynamics, quantum black holes, Schrödinger's cat paradox, the no-boundary proposal, the arrow of time, and the twistor view of space-time. This is an extremely demanding book, with many equations, and requires some knowledge of general relativity and quantum theory. The main theme of the lectures is the quantization of general relativity. Hawking's work on quantum effects near black holes and Penrose's on twistor theory have proved enormously illuminating, but few physicists, I think, believe that a full quantization of general relativity will be achieved along these paths. A better bet, surely, is string theory, despite the difficulty of developing this to the state of testable predictions. The claims made for the no-boundary proposal seem overstated. The 'prediction' of the microwave background fluctuations detected by COBE is a success also claimed by the whole generic class of inflationary theories. The debate between the positivist Hawking and the platonist Penrose on how the paradox of Schrödinger's cat should be understood is enjoyable, though the comparison with the classic debate between Einstein and Bohr in the 1920s on the correct interpretation of quantum theory, made by Michael Atiyah in his introduction, seems a bit grandiose.